In view of the problems of low appearance level and low efficiency in resistance spot welding of stainless steel rail vehicles, a new product of stainless steel rail vehicles is first developed in China, which is made by partially replacing resistance spot welding with laser welding of thin plates. The laser lap welding process of stainless steel car body is developed and the welding parameters are optimized. Under the condition of 0.6 mm spot diameter, the welded joint with qualified shear strength and quality of outer surface of lower plate can be obtained when the?laser power is 1 200 W and welding speed is 30 mm/s. By defining weld quality standard（0.9 mm penetration depth） and developing weld quality monitoring device, the laser welding manufacturing system is built, and the mass application of the new laser welding technology in high standard stainless steel rail vehicle products is realized. The weight of the stainless steel car body with laser welding reduces by 1.8 t, the lateral impact resistance of the side wall significantly improves, and the life of the car body increases by over 15%.